1. Field of the Invention
The present invention relates generally to a fluid-filled vibration damping mount adapted to exhibit a vibration-damping effect on the basis of flow of a fluid sealed therein, and more particularly to such a fluid-filled vibration damping mount that is novel in construction and suitable for use as an engine mount, a body mount or other mounts for use in automotive vehicles.
2. Description of the Related Art
A suspension-type fluid-filled vibration damping mount is known as one type of fluid-filled vibration damping mounts each interposed between two members of a vibration system for flexibly connecting these two members in a vibration-damping or isolating fashion. As disclosed in JP-A-63-167142 and JP-B-2548050, the known suspension-type fluid-filled vibration damping mount elastically supports a vibrative member, e.g., a power unit of an automotive vehicle, with respect to a subject member, e.g., a body of the vehicle, whose vibration is to be damped by suspending the vibrative member from the subject member. FIG. 15 shows an example of the known suspension-type fluid-filled vibration damping mount, by way of example, in which a first mounting member 150 attachable to the power unit and a second mounting member 152 attachable to the body are elastically connected with each other by a tapered rubber elastic body 156 disposed between the first mounting member and a lower open-end portion of a vertically extending cylindrical portion 154 of the second mounting member 152 into which the first mounting member 150 is inserted so as to extend into the cylindrical portion 154 for fluid-tightly closing the lower open-end portion of the cylindrical portion 154 of the second mounting member 152. An axially upper end portion of the cylindrical portion 154 of the second mounting member 152 is fluid-tightly closed by a flexible layer 158, whereby a fluid chamber 160 is formed between and defined by the rubber elastic body 156 and the flexible layer 158. Within the fluid chamber 160, is disposed a partition member 162 extending in a diametric direction perpendicular to an axial direction of the cylindrical portion 154 of the second mounting member 152, while being supported at its peripheral portion by the second mounting member 152. With this arrangement, the fluid chamber 160 is fluid-tightly divided by the partition member 162 into two sections, i.e., a pressure-receiving chamber 164 partially defined by the rubber elastic body 156 and an equilibrium chamber 166 partially defined by the flexible layer 158. The pressure-receiving chamber 164 and the equilibrium chamber 166 are held in fluid communication with each other through an orifice passage 168.
When such a known suspension-type fluid-filled vibration damping mount is installed in position, a static load or weight of the vibrative member, e.g., the power unit, is applied between the first mounting member 150 and the second mounting member 152 in the axial direction, and a vibrational load is primarily applied between the first and second mounting members 150, 152 in the axial direction, as well. Thus, the known suspension-type fluid-filled vibration damping mount is tuned to exhibit a damping effect based on resonance or flow of the fluid through the orifice passage 168 to vibrations applied thereto in the axial direction.
However, the known suspension-type fluid-filled vibration damping mount may be subjected to vibration applied thereto in diametric directions perpendicular to the axial direction (hereinafter referred to as “axis-perpendicular directions, where appropriate), depending upon a state of installation thereof, for example. If the suspension-type fluid-filled vibration damping mount is used as an engine mount for an automotive vehicle, for example, the engine mount may be subjected to vibrational loads applied between the first mounting member 150 and the second mounting member 152 in the axis-perpendicular directions, e.g., in a driving or a longitudinal direction of the vehicle and/or in a lateral direction of the vehicle, when the vehicle is accelerated, runs over steps, goes through corners, or experiences any other possible driving conditions. Actually, the known suspension-type fluid-filled vibration damping mount has not been sufficiently examined in its damping capability in relation to vibrations applied thereto in the axis-perpendicular directions.
In view of the above, the present inventors have conducted extensive studied and researches on damping characteristics of the known suspension-type fluid-filled vibration damping mount upon application of vibrations thereto in the diametric directions, and it has been revealed that the known suspension-type fluid-filled vibration damping mount is incapable of exhibiting a desired damping effect with respect to vibrations applied thereto in the radial directions. In particular, the suspension-type fluid-filled vibration damping mount is susceptible to be considerably deteriorated in its damping capability at around a higher frequency range of input vibrations corresponding to an acceleration noise of 300–500 Hz, e.g., booming noises and chatter noises.